In general, a water cooler is a device for cooling water supplied from a faucet or a water dispenser and providing the water to a user. Such a water cooler may be mainly installed to cool drinking water in a water purifier, a water carbonator, a cold and hot water dispenser, and the like. However, the water cooler may be utilized in various fields requiring the generation of cold water.
A method for generating cold water includes a direct cooling method in which water accommodated in a cold water tank is directly cooled using the cold water tank, and an ice thermal storage method in which cold water is generated using heat exchange with ice or a cold fluid.
Here, in the ice thermal storage method, cold water is generated by heat exchange between a cold heat-transfer material accommodated in an ice storage tank and water flowing in a heat exchange tube (cold water pipe) installed in the ice storage tank.
In this regard, a normal ice storage (ice thermal storage) cooling system includes a ice storage tank accommodating an ice storage liquid, a refrigerant tube (cooling tube) connected to a cooling unit to cool or freeze the ice storage liquid, and a heat exchange tube generating cold water by heat exchange between water and the ice storage liquid having a temperature lowered by the refrigerant tube.
Ice is formed around the refrigerant tube to a certain thickness by a low-temperature refrigerant flowing in the refrigerant tube, and the temperature of the ice storage liquid is uniformly lowered since the ice storage liquid is circulated during the process. Meanwhile, when the temperature of the ice storage liquid reaches a predetermined value or lower, the operation of the cooling unit (compressor) connected to the refrigerant tube may be stopped.
When cold water is extracted, the water flowing in the heat exchange tube exchanges heat with the ice storage liquid to be cooled, and the ice storage liquid, whose temperature is raised due to the heat exchange, melts the ice formed around the refrigerant tube, thereby having a lowered temperature through latent heat.
During the heat exchange process, since the temperature of the ice storage liquid around the heat exchange tube is lowered due to the heat exchange, sufficient circulation of the ice storage liquid is required to smoothly generate cold water using the heat exchange tube.
However, even though the normal ice storage cooling system uses a circulation pump for circulation (convection) of the ice storage liquid, sufficient cooling efficiency may not be obtained due to the limitation in a structure in which the circulation of the ice storage liquid is insufficient.